1. Field of the Invention
The present invention relates to communication systems. More particularly, the present invention relates to television signal demodulating and decoding systems.
2. Background Art
Today, with the aid of special-purpose devices or modems, personal computers can be utilized as viewing devices for television signals. Special-purpose devices or modems are required because many of the demodulating and decoding tasks that must be performed to render a television signal viewable are not effectively performed by general-purpose personal computer software. Thus, in the present state of the art, the various demodulation and decoding tasks are performed in two phases, separated by a modem-to-computer communication task. A modem will perform an initial subset of the tasks required to demodulate and decode a television signal, and then the modem will communicate the modem result to a personal computer. The personal computer will then perform of the remaining tasks in software to finish demodulating and decoding the television signal, thereby rendering it viewable for the user.
FIG. 1a illustrates conventional demodulation and decoding system 100. As shown in FIG. 1, system 100 includes television signal source 101, which broadcasts television signal 102 for reception by modem 103. Modem 103 of system 100 performs a subset of the demodulating and decoding tasks to generate modem result 104. Next, modem result 104 from modem 103 is received by personal computer 105, which performs the remaining demodulating and decoding tasks to generate viewable signal 106 to be displayed by personal computer 105 for viewing by user 107.
FIG. 1b illustrates conventional system 108 for demodulating and decoding television signals. As shown, conventional system 108 includes modem 110 and computer 120, which correspond to modem 103 and personal computer 105 of system 100, respectively. In operation, analog television signal 128 arrives at analog-to-digital converter 130 of modem 110 for demodulation and decoding. Analog-to-digital converter 130 then converts analog television signal 128 into a digital form suitable for processing by demodulator 140, by generating digital television signal 132. Demodulator 140 receives digital television signal 132 and performs a suitable demodulation on digital television signal 132, depending on the type of analog television signal 128. For instance, demodulator 140 may be able to demodulate single carrier television signals, OFDM televisions signals, or others, although in a particular implementation, demodulator 140 may only be able to demodulate one type of signal. Continuing with FIG. 1b, demodulator 140 generates demodulated television signal 142 by demodulating digital television signal 132. Subsequently, forward error correction 150 of modem 110 receives demodulated television signal 142 and applies a forward error correction (FEC) protocol to demodulated television signal 142 by, for example, utilization of a viterbi decoder or a reed-solomon decoder, thereby generating FEC television signal 152. Modem 110 provides FEC television signal 152 to computer 120 via a computer or a hardware interface (not shown), such as a PCI-e bus. As shown, computer 120 includes software decoder 160 that receives FEC television signal 152. While being executed on a processor (not shown) in computer 120, software decoder 160 performs a decoding operation on FEC television signal 152, such as MPEG decoding, to generate decoded television signal 162.
A serious drawback of conventional system 108 is that the conventional systems for demodulating and decoding television signals incur large costs for redesigning modem implementations. This is because new and different modulation schemes are being introduced on an ongoing basis, and the present division of the tasks between the modem and the personal computer in conventional systems requires new modem designs for keeping up with the evolving schemes. Therefore, there is a need in the art for a modem and computer combination that obviates the drawbacks and inefficiencies inherent in such present state of the art systems.